(1) Field of the Invention
The present invention relates generally to the dyeing of textiles and, more particularly, to a liquid alkali for use in fiber reactive dyeing of cotton and cotton blended fabrics.
(2) Description of the Prior Art
Fiber reactive dyes were first introduced in the mid 1950's. Since that time they have become a dominant factor in dyeing cotton, regenerated cellulose and blends. These dyes can also be used to dye acrylics, nylon, silk, wool and blends of these fibers. Fiber reactive dyes are easy to apply and produce brilliant shades, fastness, penetration and leveling.
Fiber reactive dyes are anionic in nature and react chemically with the fiber. The dyes include a chromophore to give color to the dye and a reactive group to form a chemical bond with the fiber. There may also be a substitutent or solubilizing group which provides additional dyeing characteristics such as solubility, substantivity, migration, washing off, etc. Fiber reactive dyes react in the presence of alkali to form a strong covalent chemical bond between a carbon atom of the dye molecule and an oxygen atom of the hydroxyl group in the cellulose. This step is called "fixing".
No single alkali system has worked on all classes of reactive dyes due to the differences in the rate of hydrolysis of each dye. Of all the alkali systems, the liquid phosphate system described in U.S. Pat. No. 4,555,348, issued to Moran, and sold under the tradename "Alkaflo" by Sybron Chemicals of Birmingham, N.J., works almost universally. But Alkaflo is high in phosphorus which can contribute to environmental problems.
Also, if the reaction mixture is too "hot" or alkaline, such as is seen with pure sodium hydroxide, the sensitive-type reactive dyes will hydrolyze with the water in the dyebath and form a nonreactive pigment that has no effect on the fabric color. Furthermore, as fashions have changed, the need to mix reactive dyes of different chemistries in the same shade and the necessity of developing a universal alkali system for cold pad batch dyeing that does not contain phosphorus has become more important.
One attempt at producing a phosphorus-free liquid alkali was recently introduced and is being sold under the tradename "REMOL FB". REMOL FB is available from Hoechst Celanese of Somerville, N.J. According to its Material Safety Data Sheet, REMOL FB contains a mixture including potassium hydroxide and sodium silicate. However, test dyeings indicated that, like pure sodium hydroxide, REMOL FB is too "hot" for many classes of dyestuffs.
Thus, there remains a need for a liquid, phosphorus-free, alkali for use in fiber reactive dyeing of cotton and cotton blended fabrics which has the clean dyeing properties of a phosphorus-based system such as Alkaflo but is not as "hot" as earlier alkali hydroxide/silicate mixtures.